The invention relates to water beds, and more particularly to an improved water mattress construction wherein all seams except the vertical corner seams are at or on the lower face of the water mattress and thus supported completely by the mattress frame which may comprise a deck or other rigid support.
A water mattress construction is shown in U.S. Pat. No. 3,952,348. In such construction, the mattress is folded from a sheet of vinyl which is substantially equal to the length and the girth of the completed water mattress. Such a construction results in four vertical seams at the corners, a lengthwise seam approximately centered on the bottom face and two horizontal seams approximately centered on the head and toe vertical ends.
Another early water mattress coonstruction is disclosed in U.S. Pat. No. 3,753,823. In this construction, the mattress is folded from an elongate vinyl sheet which is essentially double the length of the vinyl mattress, in such a way that there results one vertical side with no seam, the remaining three sides having a full-length horizontal seam that is approximately vertically centered, and four vertical corner seams.
The difficulty with both constructions is two-fold. They produce a water mattress with seams which are unsupported by the water mattress frame and support structure. And, because the seams are on the side walls relatively near the upper surface of the mattress, they will be depressed, flexed, and wrinkled when a person sits or reclines on the mattress. It has been found that this continued wrinkling of the side seams can result in their failure after a prolonged period of use.
When a water mattress fails and leakage occurs, the failure point is nearly always located on one of the side seams which is subjected to wrinkling and deformation caused by persons sitting or reclining on the water mattress. It is believed that the reason for such failures is related to a repeated pattern of wrinkle formation in the vinyl material, wherein the wrinkles extend down from the upper surface of the mattress to the seam and often remain in the material. If the sitting is repeated over a period of time, the wrinkling tends to follow a certain pattern. The repeated wrinkling pattern, together with the aging of the vinyl material and the gradual loss by evaporation or other means of plasticizers therefrom, results in a fatiguing of the vinyl material and either separation or rupture of the material at the seam.